System and Method for Cleaning Semiconductor Fabrication Equipment Parts

ABSTRACT

An exemplary embodiment discloses a process for cleaning semiconductor fabrication equipment parts with non-metallic surfaces. The process optionally includes providing a semiconductor fabrication part with a non-metallic surface to be cleaned and applying a dilute aqueous solution to remove contamination from the non-metallic surface. The aqueous solution optionally includes dilute amounts of hydrofluoric acid, nitric acid and hydrogen peroxide. The dilute amounts would optionally be in the ranges of 0.5-1.5% wt. hydrofluoric acid, 0.1-0.5% wt. nitric acid and 1-10% wt. hydrogen peroxide.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/000,586, filed Jan. 19, 2016, which is a continuation ofU.S. patent application Ser. No. 14/209,289, filed Mar. 13, 2014, whichis a division of U.S. patent application Ser. No. 13/457,750, filed Apr.27, 2012, which is a division of U.S. patent application Ser. No.11/400,125, filed Apr. 7, 2006, which is a division of U.S. patentapplication Ser. No. 10/962,359, filed Oct. 8, 2004, now abandoned,which is a divisional of U.S. patent application Ser. No. 09/927,263,filed Aug. 10, 2001, now U.S. Pat. No. 6,810,887 which issued on Nov. 2,2004 and which claims the benefit of U.S. Provisional patent applicationNo. 60/224,582, filed Aug. 11, 2000, each of which is herebyincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

The commercial fabrication of semiconductor chips is performed onsilicon wafer substrates, which are typically four to twelve inches indiameter. There are often more than 100 processing steps in thefabrication of semiconductor chips including oxidation, diffusion, ionimplantation, deposition of conductors and insulators, photolithography,and etching. Various conducting and insulating layers are depositeduniformly over the wafer to a thickness of a few microns.

In critical applications, certain new parts of semiconductor processingequipment need to be cleaned prior to installation and use in order toremove residual contamination from the machining or manufacturingprocess in order to achieve levels of cleanliness similar to thesemiconductor wafer itself. Furthermore, after many wafers have beenprocessed, the equipment used in the semiconductor processing processbecomes contaminated, and therefore unusable. For example, in an etchingmachine, polymer deposits on the outer circumference of electrodes orchucks supporting the wafers until it becomes thick enough to interferewith the wafer's contact with the electrode. This results in non-uniformetching across the wafer as well as missed transfers due to a wafersticking to polymer buildup on the electrode. Non-uniformity exceedingseven percent is beyond some specified limits, in turn affecting sidewall profile variance across the wafer. In addition, other components inthe equipment chamber e.g. roofs/domes and liners are also coated withpolymers and contaminants which contribute particles, metallic andorganic impurities to the wafers. Therefore, it is then necessary todisassemble the parts in the equipment chamber and clean the individualparts.

Generally, semiconductor manufacturing plants employ specializedcleaning houses to have the semiconductor processing equipment partscleaned. These cleaning houses typically clean the equipment byfollowing “recipes,” given to them by the manufacture of the equipment.These recipes generally include information informing the cleaning househow to clean the parts. Since, there are many variations to the waferprocesses, the polymer and contamination levels of a used chamber partis different, therefore, merely following one cleaning recipe does notalways result in the part being cleaned. In addition, after followingthe cleaning recipe, a conventional cleaning house generally will nottest the parts to ensure its cleanliness. In general, a conventionalcleaning house has no idea as to the effectiveness of the cleaningprocess provided to them in the recipe.

The result of following cleaning recipes in this manner, is that manysemiconductor parts are returned to the semiconductor manufacturingplant still contaminated with unacceptable levels of impurities. Thisresults in contamination that may be transferred onto a wafer typicallyin the form of high particle counts, or in inoperable equipment thatmust again be disassembled for re-cleaning, thus further increasing thedown time for the equipment.

In view of the forgoing, what is needed are methods and systems forenhanced cleaning and certification of semiconductor fabricationequipment. The methods should be flexible, and consistent enough tominimize or eliminate contamination from the equipment, to improve themean time between cleanings (MTBC), to improve the number of RF hoursrun on a chamber set of parts and to reduce the downtime experienced bymost semiconductor fabrication equipment.

With the ability to test and verify the effectiveness of cleaningprocedures, new cleaning methods can be developed for critical chamberparts. Critical chamber parts are usually constructed from basematerials such as ceramics (Al.sub.2O.sub.3, SiC, AlN) and quartz(SiO.sub.2). Chamber parts manufactured from these base materials arevery expensive and are selected because of they are non-contaminatingwith respect to metallics, organics and particles. With new cleaningmethods, these critical chamber parts can be effectively cleaned andrecycled to reduce manufacturing cost.

Typically, in the prior art, relatively high concentrations of acids andother cleaning agents were used to clean parts. For example, a typicalacid bath for quartz cleaning would include 1 part HF, 1 part HNO.sub.3,and 1 part H.sub.2O. Unfortunately, such high concentration solutionssuffer from a number of drawbacks. For one, they can damage the surfaceof part being cleaned by scoring, etching, pitting, etc. Further, thesehigh concentration solutions tend to be expensive, hazardous, anddifficult to dispose of.

SUMMARY OF THE INVENTION

The present invention addresses these needs by providing a process forenhanced semiconductor fabrication equipment and parts cleaning. In oneembodiment, a definition is determined that defines the characteristicsfor a clean part. Next, a part to be cleaned is tested to determine itsincoming impurity levels. A cleaning process is then determined that iscapable of reducing the incoming impurity levels for a particular part,depending on the type of base material the part is made from, thedeposits on the part, and characteristics of adhesion, particlegeneration and reactivity. The appropriate cleaning process is thenapplied to the part so that it reduces the incoming level of impuritieson the part, and tested to ensure that the part is clean. There arevarious types of impurities, but typically they fall into the categoriesof metals, particles, and organic organics.

Advantageously, one embodiment of the present invention reduces thecleaning defects by use of repeated testing of the impurity levels aftereach pass through the cleaning process. Moreover, by knowing thecharacteristics of a clean part through testing, the process of thepresent invention can achieve particular impurity level goals withincreased accuracy, and the part can be certified to meet an actualspecification based on either the need for cleanliness in thesemiconductor process, or based on statistically significant test data.Finally, the process may be continuously optimized to further enhancethe cleaning process by direct testing of the cleanliness of the part,by correlating to number of “added” particles and RF hours that theparts can be used before particles increase to unacceptable limits, andultimately by correlating to improved wafer yield.

Using the dual concepts of in-process testing of the cleanliness of apart for improved cleaning performance, and testing the cleaned partafter the final cleaning, a cleaning method can be customized,optimized, and validated for each critical part.

Advantageously, dilute chemistries can be used in preferred embodimentsof the present invention. This makes the cleaning process lessexpensive. Used chemicals are also easier to dispose of because thepercentage of acids is much lower which also in turn makes it lesshazardous. Additionally, there is less damage to the product. Thepresent invention further includes methodologies to determine optimalchemistries which are effective, yet dilute.

These and other advantages of the present invention will become apparentupon a study of the following descriptions and related drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a flowchart showing a general process guideline for cleaningsemiconductor fabrication equipment parts.

FIG. 1B is a flowchart showing a process for cleaning semiconductorfabrication equipment parts, for example high purity quartz, inaccordance with an embodiment of the present invention.

FIG. 2 is a flowchart showing a process for cleaning high purity quartzin accordance with another embodiment of the present invention.

FIG. 3 is a flowchart showing a surface particle test process forimpurity level testing of a new or clean part, in accordance with oneembodiment of the present invention.

FIG. 4 is a flowchart showing a liquid particle test process of a new orclean part, in accordance with an embodiment of the present invention.

FIG. 5 is a flowchart showing an acid extraction/ICP-MS technique of anew or clean part, in accordance with an embodiment of the presentinvention.

FIG. 6 is a flowchart showing a cleaning process 110, in accordance withone aspect of the present invention, to remove resistant organic polymerand metallic impurities from a high purity ceramic dome.

FIG. 7 is a flowchart showing a cleaning process 110, in accordance withone aspect of the present invention to remove particle from a texturedhigh purity quartz surface.

FIG. 8 is a flowchart showing a cleaning process 110, in accordance withone aspect of the present invention to remove particle and metallicimpurities from a textured high purity ceramic (>99% Al.sub.2O.sub.3)surface.

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

An invention is described herein for cleaning semiconductor equipmentparts (such as CVD and etch chamber parts) that achieve increasedeffectiveness in impurity removal. In the following description,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, tothose skilled in the art, that the present invention may be practicedwithout some or all of these specific details. In other instances, wellknown process steps have not been described in detail in order not tounnecessarily obscure the present invention. In particular, thisincludes most of the analytical testing methods used to measure orconfirm impurity levels.

In accordance with one aspect of the present invention, theaforementioned metallic impurity removal is substantially enhanced bythe use of a new chemical formula in the various cleaning processes.This cleaning formula is particularly novel as applied to the cleaningof polysilicon, quartz, and ceramic parts (Al.sub.2O.sub.3, SiC and AlN)for which it has proven to be quite effective. Specifically, thecleaning formula is a composition of high purity hydrofluoric acid (HF),nitric acid (HNO3), and hydrogen peroxide (H.sub.2O.sub.2), in verydilute quantities. Preferably, the composition includes 0.5-1.5% wt. HF,0.1-0.5% wt. HNO.sub.3, and 1-10% wt. H.sub.2O.sub.2. This particularformula results in a particularly efficient collector of metals oncertain materials as described in greater detail subsequently. This highpurity cleaning and collection solution has been shown to have very highrecoveries and efficiencies, especially on single crystal silicon wafersurfaces, high purity quartz, polysilicon, and ceramics. Previously,these materials were cleaned with concentrated chemicals mixtures ofHF/HNO.sub.3, and HCl/HNO.sub.3 at much higher concentration of 10%-40%wt for each chemical. The chemical H.sub.2O.sub.2 is not employed inthese mixtures. The high concentrations of the chemical mixtures did notimprove metallic removal and can severely etched and damaged the basematerials. It is shown that the high purity dilute chemical formula inthis invention is highly effective in removing metallic contaminants andwill not etch any of the aforementioned base materials for more than afew hundred angstroms.

It will therefore be appreciated that a dilute aqueous cleaning solutionfor parts can be made up of 0.5-1.5% wt. HF, 0.1-0.5% wt. HNO.sub.3 and1-10% wt H.sub.2O.sub.2. The concentration of H.sub.2O.sub.2 can also beno greater than about 5% wt.

Metallic contaminants form bonds with the surfaces of the semiconductorfabrication equipment parts, thus bonding the metal impurities to thesurfaces of the equipment. These chemical bonds create increaseddifficulty in cleaning the parts without the use of correct chemicalformulations. If the chemical formulations are too concentrated, thesemiconductor equipment parts can be irreversibly destroyed or are notsufficiently cleaned.

The chemical formula of the present invention substantially enhances thecleaning process by breaking the chemical bonds and thereaftercollecting the metal impurities. To elaborate further, the hydrofluoricacid breaks silicon and aluminum bonds by dissolving the silicon andaluminum oxides of the surface of the semiconductor equipment. Thisfrees the metal impurities and allows them to be collected in thecleaning solution. It should be borne in mind that the amount ofhydrofluoric acid must be carefully controlled, as too much hydrofluoricacid results in damage to the surface of the equipment parts. The use ofHF is critical in semiconductor parts cleaning because silicon andaluminum oxides are prevalent impurities in all types of parts.

The hydrogen peroxide is a strong oxidizer and is used to convert themetals such as Cu, Au and Ag into the soluble forms. Therefore, thepresence of H.sub.2O.sub.2 greatly increases the range of metalimpurities that can be removed from a surface.

Finally nitric acid is used to stabilize and increase the solubility ofsome metal impurities so that insoluble fluorides of Ca and Mg are keptin the solution and away from the surface of the semiconductor equipmentparts. In this technique, it is preferable to have the solution asdilute as possible, yet still effective to clean the equipment parts topredefined specifications. The above mentioned ranges are thus thepreferred minimums needed to clean the equipment.

The chemical formula of the present invention is used to perform variouscleaning processes for semiconductor equipment parts and other highpurity material applications. In one embodiment, this formula has beenshown to be quite effective in cleaning metal ions from high purityquartz, as is commonly found as rods, tubes, crucibles, domes, chambersand bell jars. In another embodiment, this formula has been shown to bequite effective in cleaning metal ions from high purity polysilicon andsingle crystal silicon surface, as is commonly found in chamber roofs,source rings, collars and wafers respectively. In another embodiment,this formula has been shown to be quite effective in cleaning metal ionsfrom high purity ceramic materials Al.sub.2O.sub.3 as found in chamberdomes, bell jars, rings, gas nozzle assemblies and wafer chucks; SiC asfound in chamber roofs, domes, rings and collars; and AlN as is commonlyfound in wafer chucks.

In accordance with another aspect of the present invention, theaforementioned particle impurities are removed from the semiconductorequipment surface by chemical treatments. Most semiconductor equipmentparts fabricated from the aforementioned critical base materials aretextured by grit blasting in order to improve process polymer adhesion.After machining and texturing, the parts are cleaned to removeparticles. There are two categories of particles on the texturedsurface. The first type is surface particles that are loosely adhering.These particles can be removed physically by a short ultrasonicationstep. The origin of the second category of particles is less obvious.

These particles originated from the weakened base material surfacecaused by texturing. In the process chamber, sub-surface damages areoften exaggerated during wafer processing causing particle shedding.

The chemical formula of the present invention significantly reduces theparticles from textured equipment parts by etching off a layer ofdamaged base materials without affecting the desired surface roughness.First, the depth of the subsurface damage is determined using any one ofa number of well-known techniques. Using concentrated basic solutionssuch as 10-30% wt KOH and NaOH in water, base materials such aspolysilicon base materials can be etched off to a predetermined depth(i.e. to about the depth of the measures subsurface damage) bycontrolling temperature and time to remove all the sub-surface damages.Using concentrated acidic solutions such asH.sub.2SO.sub.4/H.sub.2O.sub.2 and H.sub.2SO.sub.4/H.sub.3PO.sub.4 inthe range of 10-50% wt for each chemical, ceramic materials(Al.sub.2O.sub.3, SiC and AlN) can be etched off to a predetermineddepth by controlling temperature and time to removed all the sub-surfacedamages. In another application with quartz, the use of HF/HNO.sub.3,20-40% wt for each chemical in water, used with ultrasonic energy(27-120 kHz) for 10-20 mins is found to effectively etched off damagedquartz material resulting from grit-blasting and particle counts canthereby be drastically decreased.

In accordance with another aspect of the present invention, theaforementioned organic polymer deposited on semiconductor equipmentsurface during wafer processing can be removed from all type of criticalmaterials surface by a thermal decomposition step. Organic polymers areoften found in etch equipment parts. These organic polymers can beefficiently removed by submitting dirty quartz and Al.sub.2O.sub.3 partsto a high temperature of 600-800.degree. C. for 1-10 hours depending onhow thick or resistance the organic polymer to cleaning. A hightemperature muffle furnace is used for this purpose.

In another embodiment, disassembled semiconductor fabrication equipmentparts are subjected to cleaning processes and testing to achieveenhanced impurity removal, as described in greater detail subsequently.

FIG. 1A is a flowchart showing a general process guideline 5 forcleaning semiconductor fabrication equipment parts. The process startsat operation 10 and proceeds to operation 20 where a baseline chemistryis developed for cleaning the part. In operation 30, the part is cleanedwith the baseline chemistry. In operation 40, the effectiveness of thecleaning process is tested. If it is not sufficient, operation 50 isperformed where the chemistry is adjusted to improve the cleaningability and the part is re-cleaned at operation 30. If the firstcleaning was effective, the process ends at operation 60.

In operation 50, the chemistry can be adjusted in various ways. Forexample, the chemistry can be changed by adding or deleting acids,oxidizers, etc. It can also be adjusted by increasing the concentrationof the solution, or by making the solution more dilute. The purpose ofoperation 50 is, therefore, to optimize the chemistry to provide themost effective, least damaging, most economical, and least hazardoussolution to cleaning the part.

FIG. 1B is a flowchart showing a process 100 for cleaning semiconductorfabrication equipment parts, for example high purity quartz, inaccordance with an embodiment of the present invention. In an initialoperation 102, pre-process operations are performed. Pre-processoperations include preparing and testing facility configurations andother pre-process operations that will be apparent to those skilled inthe art. In particular, pre-process operations can include establishingenvironmental controls (e.g. particles and metals in the environment),qualifying RO/DI high purity water, establishing “new” handlingprotocols, and setting up fixturing process.

In a specification operation 104, the specification for what constitutesa clean part is determined. As indicated previously, conventionalcleaning houses generally follow a recipe given to them by amanufacturer. For example, a cleaning recipe from a manufacturer mayinclude rinsing a part in deionized water, immersing it in a particularchemical mixture, etc. In the present invention, instead of merelyfollowing a cleaning recipe, a specification for a clean part isdetermined. The specification characterizes what the minimum parametersare for a particular part to be considered clean enough to achieve therequired wafer performance.

A specification may be obtained from another party, such as the partyowning the part to be cleaned, or the specification may be determined bytesting. There are three ways to create a specification through testing.In the first approach a part is first obtained that is already known tobe clean, i.e., has the minimum parameters to be considered clean, forexample a new part. The part is then tested and characterized withrespect to particles, metals, organics, or any combination thereof. Whencharacterizing with respect to particles, the surface of the part isexamined with respect to particles using several different analyticaltechniques which may include the Dryden QIII surface particle counter, aliquid particle counter (LPC), or Scanning Electron Microscopy (SEM) orSEM with Energy Dispersive X-ray detection (SEM/EDX). Whencharacterizing with respect to metals, the surface is examined throughsophisticated analytical chemistry testing methods with respect tosurface metal contamination, bulk metal contamination, or both. Whenexamining the part with respect to bulk metal contamination, a portionof the material is digested in a solution to measure the impuritieswithin the material. With respect to surface metal contamination, metalsare extracted from the surface, normalized to the surface area, andmeasured by spectroscopic techniques such as inductively coupledplasma-mass spectrometry (ICP-MS). When characterizing the part withrespect to organics, surface extractions may be made using DI andsolvents that are then analyzed by a total organic carbon analyzer (TOC)and Gas Chromatography (GC) or Gas Chromatography with Mass Spectrometry(GCMS) respectively. Alternately or additionally, the entire materialmay be outgassed at a high temperature with the resulting gasses beinganalyzed by dynamic head space GC-MS or ATD GC-MS.

In the second approach, new or used parts are cleaned using the bestknown cleaning methods based on historical or theoreticalconsiderations. After the cleaning process is applied, the part istested for impurities. The part is then assembled into the semiconductorprocess equipment and chamber process data is collected. Process datamay include 1) particles added (“adders”) to a silicon wafer surfaceafter being in contact with the process equipment containing the cleanpart; 2) metal impurities transferred onto a silicon wafer surface afterbeing processed in the semiconductor equipment containing the cleanpart; 3) mean number of wafers between cleanings; etc. Such chamberprocess data can then be correlated to analytical impurity test datafrom the cleaned part itself. In this way cleaning methods and formulascan be developed or improved based on the correlation between the testdata from the analytical impurity testing on the part and the datagenerated after running a wafer in the process chamber. Moreover, aspecification can be set after evaluation of the chamber processperformance parameters.

In the third approach, specifications can be set by collecting impuritytest data on a statistically significant number of parts that has provento perform well in the semiconductor process. Control limits can also beestablished by collecting test data on a statistically significantnumber of parts.

Next, in an operation 106, the incoming impurity level for the part isdetermined. In this operation, a part is tested to determine the currentimpurity level. of the part with respect to metals, particles, ororganics. For particles, this determination is made by performing eithera surface particle test or a liquid particle count test, as described ingreater detail subsequently. Depending on the type of test utilized todetermine the particle level, the particle impurities are described aseither particles per cm.sup.2 or particles per volume of solution. Theincoming trace metal impurities are typically measured using acidextraction ICP-MS technique, the metallic levels are described asatoms/cm.sup.2 or ng/cm.sup.2. The incoming impurity levels for organicsare measured using GC, GCMS, or ATD GCMS and the organic levels aredescribed as atoms/cm.sup.2 or ng/cm.sup.2 for trace concentration or %surface concentration for major concentration. SEM/EDX maybe usedsemi-quantitatively for the determining of major elements such as thosepresent in the process polymers, the elements being C, F, Cl, Al Si andO.

In a surface determination operation 108, the surface of the part ischaracterized. Generally, this operation determines the characteristicsof the material. These characteristics include the desired surfacefinish as well as surface roughness.

Referring next to operation 110, a mechanical and chemical process thatwill meet the clean specification of the part is determined. Dependingon the material, size, condition, and specification of the part beingcleaned, a mechanical and chemical process is determined that will cleanthe part to the predefined clean specification of operation 104. Forexample, a process for cleaning a quartz part is disclosed subsequently.Once determined, the chemical and/or mechanical processes are applied tothe part.

After cleaning, the part is again tested to determine the impurity levelof the part, in operation 112. This operation is performed much the sameas operation 106, the difference being that operation 112 is carried outafter the part is cleaned.

A determination is then made as to whether the clean specification hasbeen met, in operation 114. Essentially, the results of the impuritylevel determination operation 112 are compared to the specification,determined in operation 104. If the specification has been met, theprocess continues with an equipment testing operation 116. However, ifthe specification is not met, the process continues with another processdetermination operation 110.

Thus, the present invention, with respect to metal impurities, utilizesa sequential approach to cleaning semiconductor equipment parts. In thismanner, the cleaning process is repeated until the impurity level isbrought down to an acceptable level. Essentially, the impurity levelsare brought down by orders of magnitude in a stepwise fashion. Inaddition, the cleaning processes can be optimized with each pass throughthe process, based on the measurement of the impurity levels.

In an equipment test operation 116, the clean equipment part isinstalled and operated with the process for manufacturing semiconductordevices and the wafers are measured for contaminants after being run inthe process as an indication of the purity of the materials in thechamber. Particularly, the number of particles added to the wafer afterrunning the process and the impurities on the wafers are consideredindicies.

A decision is then made as to whether the part functions properly in itsrelated equipment, in operation 118. If the part functions properly, theprocess is completed in a finishing operation 120. Otherwise, theprocess continues with another process determination operation 110.

Finally, in a finishing operation 120, the cleaning process is completedand the cleaned part may be put back into production. Advantageously,the present invention reduces cleaning defects by repeated testing ofthe impurity levels after each pass through the cleaning process.Moreover, by knowing the characteristics of a clean part, the process ofthe present invention can achieve specified results with increasedaccuracy. Finally, the cleaning process may by continuously optimized toachieve a cleaning process that cleans close to 100% of the parts from aparticular process.

An important feature of the present invention is the use of analyticaltesting. As described previously, conventional cleaning is done withlittle or no testing of the part itself. The most testing typically donein conventional cleaning is testing of the resistivity of the rinsewater used in a conventional cleaning process or of the concentrationsof the acid baths. In contrast, the present invention consistently testthe impurity levels of the semiconductor parts after being cleaned, asdescribed in greater detail with respect to FIG. 3.

In view of the foregoing, it will be appreciated that a process forcleaning semiconductor fabrication equipment parts includes determininga definition for a clean part including multiple maximum acceptableimpurity levels, determining an initial multiple impurity levels of apart prior to its cleaning, determining a cleaning process to apply tothe part, applying the cleaning process to the part, wherein thecleaning process creates reduced multiple impurity levels for the partbelow that of the initial multiple impurity levels, determining thereduced multiple impurity levels, comparing the reduced multipleimpurity levels against the multiple maximum acceptable impuritieslevels of said definition, and repeating the application of the cleaningprocess to the part if said reduced multiple impurity levels do not meetthe definition of a clean part.

The process can also include testing the part in reassembled equipmentin which the part was designed to operate and repeating a cleaningprocess on the part if the part does not function properly in thereassembled equipment.

Also the process can include at least one impurity level which isdetermined utilizing a surface particle test. The impurity level canalso be determined by using a liquid particle test. Also, one or moreimpurity levels can be determined by using acid-extraction ICP-MStechnique.

FIG. 2 is a flowchart showing a process for cleaning high purity quartzin accordance with another embodiment of the present invention. FIG. 2shows a process 200 that progresses through the following acts oroperations. In 210 the part is degreased with solvents such asIPA/acetone and is sprayed rinse with DI water or alternatelyultrasonicated in DI water. In 212 the part is cleaned by either a sprayor squirt rinse with the aforementioned high purity cleaning formula. In214 the cleaning solution used in 212 is discarded. In 216 the acts oroperations of 212 and 214 are repeated, where the number of repeats is afunction of specification level of purity. In 218 another DI waterultrasonication and spray rinse of the quartz part is performed. In 220the part is allowed to dry under heat lamps within a controlledHEPA/ULPA filtration cleanhood located in a cleanroom. In 222 testing isperformed for surface metals and/or surface particles. In 224 impuritydata is collected. And in 226 the quartz part is packaged in a cleanroomor similar controlled environment.

It will therefore be appreciated that a method for reducing sub-surfacedamage to a part includes determining how deep is the sub-surface damagebeneath a surface of a part, chemically etching the surface of the partand stopping the chemical etching of the surface at about the depth ofthe sub-surface damage.

Also, a method for cleaning a part includes performing anultrasonication cleaning process to a surface of a part to be cleaned,spray rinsing the part with a dilute chemical mixture and spray rinsingthe part with deionized water. The method can also include repeating thespray rinsing of the part with a dilute chemical mixture and sprayrinsing the part with deionized water based upon the specification ofpurity for the part.

FIG. 3 is a flowchart showing a surface particle test process 300 forimpurity level testing of a new or clean part, in accordance with oneembodiment of the present invention. In an initial operation 301,pre-process operations are performed. Pre-process operations includedetermining the specification of characteristics for a clean part, andother pre-process operations that will be apparent to those skilled inthe art. This process is applicable, for example, to operations 1-6 and112 of FIG. 1.

Next, in a cleanroom operation 302, the semiconductor equipment part tobe measured is opened in a class 1000 cleanroom or better (1000particles per cubic centimeter). Upon being disassembled, semiconductorequipment part is packaged for delivery to the cleaning center. To avoidfurther contamination of a new or clean part, it is preferable to openthe part in a controlled clean environment. In 304 the input of theparticle counter is scanned over the part over a specified distant. In306 an analysis of the part is begun using clean handling techniques. In308 impurity data is collected after stabilization, and in 310 the datais processed. The process is completed in 312.

FIG. 4 is a flowchart showing a liquid particle test process 400 of anew or clean part, in accordance with an embodiment of the presentinvention. In an initial operation 401, pre-process operations areperformed. Pre-process operations include determining the specificationof characteristics for a clean part, and other pre-process operationsthat will be apparent to those skilled in the art. This process isapplicable, for example, to operations 1-6 and 112 of FIG. 1.

Next, in a cleanroom operation 402, the semiconductor equipment part tobe cleaned is opened in a cleanroom. Upon being disassembled,semiconductor equipment is packaged for delivery to the cleaning center.To avoid further contamination of the part, it is preferable to open thepart in a controlled clean environment.

In a UPW control operation 404, the particles currently present in theultra pure water are measured. The liquid particle test process 400 usesultra pure water (UPW) as the carrier medium to determine the impuritylevel for a particular semiconductor equipment part. As a control, thelevel of particles present in the UPW is determined before the part isplaced in the water. Subsequently, the new part can be ultrasonicated todislodge particles that are adhered to its surface into the UPW The UPWcan then be retested, with the particle count difference beingattributable to the part itself.

In a UPW application operation 406, a known volume of the UPW is appliedto a cavity of the part to be analyzed. The cavity of the part isessentially the area of the part which provides the best test area foranalyzing the impurity level of the part.

Next, in a UPW extraction operation 408, the UPW is extracted from thepart and introduced into a liquid particle counter. After introducingthe UPW to the cavity of the part, the UPW gathers particles from thesurface of the part. Thus, by knowing the particle level of the UPWbefore being introduced into the cavity of the part, and then measuringthe amount of particles in the UPW after being introduced into thecavity of the part, the impurity level of the part can be determined.

The analysis of the impurity level for the part is then begun, in ananalysis operation 410.

Then, after the liquid particle counter stabilizes, the impurity leveldata is collected, in a data collection operation 412. Initially, thedata is collected in particle size. Thereafter, the data is normalizedover the surface area of the semiconductor part being analyzed.

The impurity level data is then processed in a data processing operation414. The particles are measured both in terms of size distribution andquantity. The quantity could be in thousands of counts down to singledigits. The distribution can be as low as about 0.05 microns up to about10 microns. Preferably, the particle counts are “bucketed” intospecified size ranges of interest to assist in analysis. The result isthe number of particles per volume of solution or particles percm.sup.2.

Finally, post-process operations occur in operation 416. Post-processoperations include using the impurity level information to aid infurther processing of the part and other post-process operations thatwill be apparent to those skilled in the art.

In view of the foregoing, a method for determining contamination of anopenable part having inner surfaces includes introducing a part into acontrolled clean environment of at least class 1000, opening the part inthe controlled clean environment and running contamination analysis onthe inner surfaces of the part.

The method can also include applying a known volume of ultra pure waterto a cavity of a part, extracting the water, and analyzing contaminantsfound in the water. The method can additionally include applying a knownvolume of a high purity extraction solution to a cavity of a part,extracting the extraction solution, and analyzing contaminants found inthe extraction solution.

FIG. 5 is a flowchart showing an acid extraction/ICP-MS technique 500 ofa new or clean part, in accordance with an embodiment of the presentinvention. In an initial operation 501, pre-process operations areperformed. Pre-process operations include determining the specificationof characteristics for a clean part, and other pre-process operationsthat will be apparent to those skilled in the art. This process isapplicable, for example, to operations 1-6 and 112 of FIG. 1.

Next, in a cleanroom operation 502, the semiconductor equipment part tobe cleaned is opened in a cleanroom. Upon being disassembled,semiconductor equipment is packaged for delivery to-the cleaning center.To avoid further contamination of the part, it is preferable to open thepart in a controlled clean environment.

In an acidic extraction control operation 504, the analytical testprocess 500 uses a high purity extraction solution (e.g. 1.25% wt HF, 3%wt H.sub.2O.sub.2 and 0.125% wt HNO.sub.3) to determine the metallicimpurity level for a particular semiconductor equipment part. As acontrol, the level of metallic impurities present in the extractionsolution is determined by ICP-MS. Subsequently, a selection area of thenew part is extracted with the high purity extraction solution. Theextract is then retested, with the metallic level difference beingattributable to the part itself.

In a operation 506, a known volume of the high extraction solution isapplied to a cavity of the part to be analyzed. The cavity of the partis essentially the area of the part which provides the best test areafor analyzing the impurity level of the part.

Next, in a operation 508, the high purity extraction solution isextracted from the part and introduced into an ICP-MS. After introducingthe high purity extraction solution to the cavity of the part, theextraction solution gathers metallic impurities from the surface of thepart. Thus, by knowing the metallic level of the extraction solutionbefore being introduced into the cavity of the part, and then measuringthe amount of particles in the extraction solution after beingintroduced into the cavity of the part, the impurity level of the partcan be determined. The acid extraction/ICP-MS technique is thencompleted with operation 510.

The analysis of the impurity level for the part is then begun, in ananalysis operation 510.

Then, after the ICP-MS stabilizes, the impurity level data is collected,in a data collection operation 512. Initially, the data is collected inppbw (parts per billion wt). Thereafter, the data is normalized over thesurface area of the semiconductor part being analyzed.

The impurity level data is then processed in a data processing operation514. The metallic impurities are measured both in terms of concentrationin ppbw for each type of trace metals. The area of the part that isextracted is calculated and the result is normalized atoms per cm.sup.2or ng/cm.sup.2.

Finally, post-process operations occur in operation 516. Post-processoperations include using the impurity level information to aid infurther processing of the part and other post-process operations thatwill be apparent to those skilled in the art.

FIG. 6 is a flowchart showing a cleaning process 600, in accordance withone aspect of the present invention, to remove resistant organic polymerand metallic impurities from a high purity ceramic dome (>99%Al.sub.2O.sub.3). In an initial operation 601, pre-process operationsare performed. Pre-process operations include determining the particularcharacteristics of the part to be processed and other pre-processoperations that will be apparent to those skilled in the art.

In operation 602, the ceramic dome is DI water sprayed rinse to removeloose polymers, particles and metallic impurities. Initially, theceramic dome is unpacked, recorded, and photographed to record theinitial condition of the dome. The ceramic dome is then placed in achemical bath 603 for about 2 hours. The chemical bath is preferably andilute HF/HNO.sub.3 chemical bath, which is heated to about60-80.degree. C. The concentration of HF is less than 5% wt andHNO.sub.3 is less than 10% wt. The hot acid dissolves Si—O and Al—Obonds and breaks other metallic bonds. Thereafter it is removed from thechemical bath, DI spray rinsed and dried with a cleanroom wipe or with aheat lamp until no moisture is observed on the inside or outside of thedome. It has been found to be very important to do the pre-treatmentstep 603 before putting the part into the furnace in order to dissolvethe Si—O and Al—O bonds. This advantageously reduces the amount time thepart has to be in the furnace of the next operation.

In a heating operation 604, the dome is heated in a furnace. In thisoperation, the dome is placed in a furnace and heated to about700-800.degree. C. for about 6-12 hours. After about 6-12 hours, thefurnace is turned off. To avoid damage to the dome, the furnace shouldgenerally not be opened until the temperature reaches below 200.degree.C. Opening the furnace earlier may result in the dome being cracked.After the temperature reaches below 200.degree. C., the furnace may beopened and allowed to cool to below 80.degree. C. The dome is thenwithdrawn from the furnace when the temperature reaches below 80.degree.C.

Next, in a bath operation 606, the dome is placed in another chemicalbath. The chemical bath is also an HF/HNO.sub.3 chemical bath, which isheated to about 80.degree. C. The concentration of HF and HNO.sub.3 isthe same as the first bath but is kept clean and is prepared from higherpurity chemicals. The dome is placed in the chemical bath for about 6-8hours to dissolve any residual carbon and silicon/aluminum oxides andany other metallic impurities. After this step, it is placed in an acidwaste tank and rinsed with deionized water to remove any residual acids.Thereafter, the dome is preferably visually inspected 607 to determinethe cleanliness of the part. If organic polymer is still observed, theoperations 604/606 are repeated.

In an ultrasonication operation 608, the dome is ultrasonicated indeionized water. Once a visual inspection has been made of the dome, itis ultrasonicated in a fresh overflowing deionized water bath for abouttwo hours. In the operation 610, the dome is tested by LPC technique. Asstated previously, this impurity testing operation helps in determiningwhether the part has been cleaned to have characteristics in accordancewith the predetermined clean specification. If the particle level asmeasured by LPC technique is less than 400,000 particle per cm.sup.2,the dome is then rinsed in deionized water approximately 10 times, andthereafter purged dry with filtered N.sub.2 and further under a heatlamp 611 for at least 1 hour. The process 608 can be repeated if thedome has not attained the specified levels of impurity

The part is then further tested for impurities, in a testing operation612. Preferably, a surface particle test is performed on the dome usinga Dryden QIII particle counter. After testing adequately to thepredetermined specification, the part is packaged with cleanroom doublebags in the cleanroom.

Finally, in operation 614, various post-process operations areperformed. Post-process operations include testing the dome in fullyassembled semiconductor fabrication equipment, and other post-processoperations that will be apparent to those skilled in the art. After thepost-process operations are completed, process 600 is completed withoperation 616.

It will therefore be appreciated that a method for cleaning ceramicparts includes immersing a ceramic part into a first chemical bath todamage contaminant bonds, heating the ceramic part in a furnace afterthe contaminant bonds are damaged and immersing the ceramic part in asecond chemical bath to remove contaminants. Also, the first chemicalbath can be a dilute chemical bath including HF and HNO.sub.3 which isheated to about 60-80.degree. C.

FIG. 7 is a flowchart showing a cleaning process 700, in accordance withone aspect of the present invention to remove particle from a texturedhigh purity quartz surface. In an initial operation 701, pre-processoperations are performed. Pre-process operations include determining theparticular characteristics of the part to be processed and otherpre-process operations that will be apparent to those skilled in theart.

In an operation 702, the high purity quartz part is DI water sprayrinsed to remove loose polymers, particles and metallic impurities.Initially, the quartz part is unpacked, recorded, and photographed torecord the initial condition of the dome. The quartz part is then placedin a chemical bath 703 and ultrasonicated for 15 min. The chemical bathis preferably a concentrated HF/HNO.sub.3 chemical bath. Theconcentration of HF is about 25% wt and HNO.sub.3 about 35% wt. Theconcentrated acid in the presence of ultrasonication energy dissolves alayer of damaged quartz to-lower the particle counts on the quartz partsurface. Thereafter it is removed from the chemical bath and DI sprayrinsed in an operation 704.

Next, in a DI ultrasonication operation 706, the quartz isultrasonicated in deionized water to further remove particles. Once avisual inspection 707 has been made of the quartz part, it isultrasonicated in a fresh deionized water bath 707A for 15 min. If thepart does not pass the visual inspection test, the part goes back tooperation step 703 for additional cleaning. In the operation 708, thequartz is tested by LPC technique. As stated previously, this impuritytesting operation helps in determining whether the part has been cleanedto have characteristics in accordance with the predetermined cleanspecification. If the particle level as measured by LPC technique isless than 200,000 particle per cm.sup.2, the quartz part is then rinsedin deionized water approximately 10 times, and thereafter purged drywith filtered N.sub.2 and further under a heat lamp for at least 1 hourin an operation 710. The process 706 can be repeated if the dome has notattained the specified levels of impurity.

The part is then further tested for impurities, in a testing operation712. Preferably, a surface particle test is performed on the dome usinga Dryden QIII particle counter. After testing adequately to thepredetermined specification, the part is packaged with cleanroom doublebags in the cleanroom.

Finally, in operation 714, various post-process operations areperformed. Post-process operations include testing the dome in fullyassembled semiconductor fabrication equipment, and other post-processoperations that will be apparent to those skilled in the art. After thepost-process operations are completed, process 700 is completed withoperation 716.

FIG. 8 is a flowchart showing a cleaning process 800, in accordance withone aspect of the present invention to remove particle and metallicimpurities from a textured high purity ceramic (>99% Al.sub.2O.sub.3)surface. In an initial operation 801, pre-process operations areperformed. Pre-process operations include determining the particularcharacteristics of the part to be processed and other pre-processoperations that will be apparent to those skilled in the art.

In an operation 802, the ceramic dome is DI water sprayed rinse toremove loose polymers, particles and metallic impurities. Initially, theceramic dome is unpacked, recorded, and photographed to record theinitial condition of the dome. The ceramic dome is then placed in achemical bath 803 for about 2 hours. The chemical bath is preferably aconcentrated H.sub.2SO.sub.4/H.sub.2O.sub.2 orH.sub.2SO.sub.4/H.sub.3PO.sub.4 chemical bath, which is heated to about140-180.degree. C. The concentration of H.sub.2SO.sub.4 is about 50% wt,H2O2 is about 15% wt and H.sub.3PO.sub.4 about 40% wt. The hotconcentrated acid dissolves a layer of damaged alumina to lower theparticle counts on the dome surface. Thereafter it is removed from thechemical bath and DI spray rinsed in an operation 804.

Next, in a bath operation 806, the dome is placed in another chemicalbath. The chemical bath is a dilute HF/HNO.sub.3 chemical bath. Theconcentration of HF and HNO.sub.3 is less than 5% wt and 10% wtrespectively to remove metallic impurities. After this step, it isplaced in an acid waste tank and rinsed with deionized water to removeany residual acids. Thereafter, the dome is preferably visuallyinspected 807 to determine the cleanliness of the part. If the partstill needs more cleaning, operation 806 is repeated.

In an ultrasonication operation 808, the dome is ultrasonicated indeionized water. Once a visual inspection has been made of the dome, itis ultrasonicated in a fresh overflowing deionized water bath for abouttwo hours. In the operation 810, the dome is tested by LPC technique. Asstated previously, this impurity testing operation helps in determiningwhether the part has been cleaned to have characteristics in accordancewith the predetermined clean specification. If the particle level asmeasured by LPC technique is less than 500,000 particle per cm.sup.2,the dome is then rinsed in deionized water approximately 10 times, andthereafter purged dry with filtered N.sub.2 and further under a heatlamp for at least 1 hour in an operation 812. The process 808 can berepeated if the dome has not attained the specified levels of impurity.

The part is then further tested for impurities, in a testing operation814. Preferably, a surface particle test is performed on the dome usinga Dryden QIII particle counter. After testing adequately to thepredetermined specification, the part is packaged with cleanroom doublebags in the cleanroom.

Finally, in operation 816, various post-process operations areperformed. Post-process operations include testing the dome in fullyassembled semiconductor fabrication equipment, and other post-processoperations that will be apparent to those skilled in the art.

In view of the foregoing it will be appreciated that a method forcleaning textured quartz parts includes immersing a textured quartz partinto an ultrasonic chemical bath, immersing the textured quartz partinto an ultrasonication water bath and immersing said textured quartzpart into a deionized water bath. The method can also include immersingthe part in an ultrasonification overflowing bath.

It will further be appreciated that a method for determining thecleanliness of semiconductor fabrication equipment parts includestesting the parts before a cleaning process for at least one ofparticles, metallic impurities and organics. The parts are tested aftercertain steps in the cleaning process for at least one of particles,metallic impurities and organics. The parts are tested a final timeafter a final cleaning step for at least one of particles, metallicimpurities and organics.

Also, a method for removing particles on a textured surface of asemiconductor fabrication equipment part includes determining a chemicalbonding characteristic of the particles, identifying a type of particlesembedded in the textured surface, measuring a depth of any subsurfacedamage and performing a combination of ultrasonication and chemicaletching to the textured surface.

While the present invention has been described in terms of severalpreferred embodiments, there are many alterations, permutations, andequivalents which may fall within the scope of this invention. It shouldalso be noted that there are many alternative ways of implementing themethods and apparatuses of the present invention. It is thereforeintended that the following appended claims be interpreted as includingall such alterations, permutations, and equivalents as fall within thetrue spirit and scope of the present invention.

1. A method for removing particles on a textured surface of asemiconductor fabrication equipment part comprising: determining achemical bonding characteristic of the particles; identifying a type ofparticles embedded in the textured surface; measuring a depth of anysubsurface damage; and performing a combination of ultrasonication andchemical etching to the textured surface based upon said chemicalbonding characteristics, said type of particles and said depth ofsubsurface damage.